Donald Trump has signed a new executive order preventing citizens of six Muslim-majority countries from entering the US for the next 90 days. The decree covers Syria, Iran, Sudan, Somalia, Libya and Yemen, but it will not apply to visa holders or dual citizens. Refugees will be denied entry to the country for a period of 120 days.

Beyond the effects that the new ban will have on people from the Middle East and North African region, it also has serious repercussions for science. Trump’s travel prohibitions are an integral part of a broader ideology that is at war with rational critical thought. It is from that perspective that my scientist colleagues and I find ourselves most concerned.

An attack on scientists

The United States today is the world’s leading scientific research hub, and the largest producer of skilled scientists and engineers. It is difficult to estimate what percentage of the world’s active scientists are US-trained, but it is well documented that somewhere between 30% and 50% of US-trained scientists and engineers at the PhD level are foreign-born.

Many of these highly talented individuals return to their countries to support development at home. Many remain in the US to become the researchers, engineers, medical doctors and tech-entrepreneurs that fuel the economy there.

Many scientists are now wondering whether, in solidarity with their banned colleagues, they should boycott US conferences and refuse invitations to speak in the country. Others believe this to be counterproductive, and the debate rages. Both sides make excellent points, and the answer is not simple.

What is clear is that if the proposed isolationist and discriminatory policies continue, a scientific boycott would have strong moral and political justification, comparable to that of other boycott movements that protest against discriminatory policies all over the world.

An attack on science

The travel ban is detrimental to scientific exchange and progress in the US and possibly globally – not just because it is potentially based on bad data. However, there is a far greater menace underlying its ethos, and that of the Trump administration.

From a scientific perspective, it is tragic. Science is a process of generating facts (we call them data). In science there are no alternative facts. There may be alternative interpretations of the same facts, but not alternative facts.

Without confidence in facts, there can be no meaningful debate on interpretation, and thus no progress. It is a fact that the planet is warming. It is also a fact that human activity contributes significantly to that warming. Scientists may debate how to tackle these changes, and which model will best predict future effects. However, they do not disagree on the facts.

And science is much more than the collection of data. It is a process of analysis and discussion of data. It is the process that allows rational thought, open debate and the evolution of understanding to rule over personal preferences, individual biases and ideological positions.

This is not the monopoly of people in white coats who speak weird jargon and drink too much coffee. Science is the prerogative of every person in the world. It is what sustains freedom of exploration, respect for positive debate and acceptance of a better idea based on proof.

This is what the language and attitude of the current US administration seeks to undermine.

The travel ban imposed by the US administration is one symptom of a wider and more dangerous assault on fundamental values of rational thought, evidence-based opinion making and debate.

It is a great irony that we are witnessing attacks on both fact and people from the Middle East and North African region, given that the father of the scientific method is the great scientist and mathematician Ibn Al-Haytham, who just happened to hail from what is today Iraq.

The core values I have mentioned are key to scientific research, but they are also integral to modern democracy and respect for human dignity and equality. As such, they are worth standing up for by all of us, most of all by scientists.